Project Summary/Abstract The long-term goals of our research are to describe the age trajectories of sleep, sleep EEG, and sleep need, focusing on changes across and through adolescence. Achieving these goals will help fill major gaps in our knowledge, gaps which have direct and important implications for both public health and developmental neuroscience. Insufficient sleep and daytime sleepiness are associated with impaired physical and mental health and behavioral problems. Insufficient sleep is particularly critical during adolescence because of the profound reorganization of the human brain that takes place over the second decade of life. Despite its importance, we lack basic evidence on the quantitative relations of adolescent sleep durations to daytime sleepiness and performance. The recently released American Academy of Sleep Medicine consensus statement on adolescent sleep need was necessarily based mainly on post-hoc studies that showed correlations between poor sleep habits and impaired health and performance. Our proposed project will extend our ongoing prospective dose-response studies of the effects of varied sleep durations on daytime cognitive function, daytime sleepiness and sleep EEG patterns. The first 3 years of this study (spanning ages 10-16 years) revealed a number of interesting findings, including a divergence in the age effects of sleep duration on daytime sleepiness and daytime performance. The Continuing Renewal will extend our studies from mid-adolescence through young adulthood and allow us to determine whether the changes we observed thus far are transient maturational events or continue into adulthood. In addition to expanding the age range, the proposed continuation adds new measures and new methods of analysis of the effects of sleep duration effects on cognition. With the new additional data, the expanded study will span ages 10 to 23 years. By including the transition to young adulthood we can test rigorously the important basic science question of whether the adolescent changes in sleep duration-daytime sleepiness and performance relations are correlated with the steep adolescent decline of delta power in the NREM EEG; this decline is the most massive brain change of adolescence that can be measured non-invasively. The proposed studies will provide the first systematic longitudinal dose-response data on sleep need across this age range. Such data will begin to address the urgent need for evidence-based public health recommendations for adolescent sleep durations. Understanding the basic causes of daytime sleepiness in adolescence is a major goal of the National Center on Sleep Disorders Research of the National Heart Lung Blood Institute. The proposed studies will advance that understanding by providing the first longitudinal description of changes in sleep EEG and sleep need from late childhood through adolescence and into young adulthood. These data will also bear on the neuroscience of adolescent brain maturation.